bridget moynahan1 blue bloo 'Blue Bloods' Season 4, episode 20: Erin grapples with two kinds of 'Custody Battle'

One type of custody involves parents and children, and another involves police and suspects.

Erin (Bridget Moynahan) had to deal with both at once in “Custody Battle,” Friday’s (April 25) episode of CBS’ “Blue Bloods” written by executive producer Ian Biederman. The events began with an effort by agitated Christopher Collins (guest star Brent Werzner) to see his daughter Alex (guest star Karlin Biederman, daughter of the writer-producer), who resided with her mother Frannie Ferguson (guest star Angela Sarafyan).

The parents’ loud debate in the street drew Jamie (Will Estes) and Eddie (Vanessa Ray) to the scene, where they arrested Collins for disorderly conduct — which Frannie protested, maintaining that cops “only make things worse.”

Back at the precinct, as Eddie lamented being painted as one of “the bad guys,” Officer Kara Walsh (guest star Tonya Glanz) yelled for help for her partner Cutter (guest star Charlie Semine), who had accompanied Collins to the men’s room. Jamie found Collins unconscious on the floor and started CPR — but, as Cutter claimed that Collins had attacked him, it was too late.

As he left a press conference about the death, Frank (Tom Selleck) was grilled by reporters, one of whom inquired whether Erin handling the investigation for the D.A.’s office was “a glaring conflict of interest.” Grousing about being “ridiculously asked” that question, Frank insisted his daughter could stay objective.

Erin began her probe with Frannie, who accused Cutter by claiming “that crazy cop killed” Collins. And since there had been no eyewitnesses other than police officers, Frannie added, “We both know what’s gonna happen here.”

After encouraging Cutter to “hang in there” in the precinct locker room, Jamie found protesters yelling about police brutality outside the station. Eddie mentioned she’d seen Frank’s press conference on TV, and Jamie noted how Frank sticks up for others — to which Eddie said she couldn’t count on her own dad, who had just written her from the prison where he was doing time for a Ponzi-like financial scheme.

Erin met Frank at his office, planning to go out to dinner … but he had ordered in for them, reasoning that it wasn’t “a good idea for you and me to be out on the town,” being on opposite sides of the Cutter investigation.

Their conversation about the case quickly grew heated, with him telling her, “Your participation complicates an already difficult situation.” She retorted that it worked “both ways” since her father was the police commissioner, and she stated that wouldn’t keep her from prosecuting one of his officers as she left angrily.

Erin’s mission appeared sealed the next day when medical examiner Craig Esterbrook (guest star Tibor Feldman) said a brain injury from being choked was what killed Collins. “You’ve got an old-fashioned homicide on your hands,” Esterbrook told her.

Cutter was Erin’s next interviewee, and he maintained he never put his hands on Collins’ throat. “I’m sick about what happened,” he said, “but if I hadn’t defended myself, it would have been me dead in that bathroom.” Officer Walsh came in next and confirmed Cutter’s claims to Erin.

Afterward, Erin went to tell Frannie that Collins’ death had been ruled a homicide. Explaining that Alex was “everything to him,” Frannie said the street argument had been about her possible move to Chicago with the child. “He didn’t deserve to die for loving his little girl,” Frannie added, clearly striking a note with Erin.

Jamie informed Eddie he’d accepted an assignment for them to take a testifying convict back to prison — the prison where Eddie’s father happened to be. She sternly told Jamie, “I know you think you’re helping. You’re not.” She insisted she had no need to speak to her father and said, “If I need someone to fix my life, I’m gonna call a shrink. Not a cop.”

Frank summoned Cutter’s former Long Island police chief, Norm Valenti (guest star Vincent Curatola), to come in and discuss Cutter’s record. Valenti vouched for him and said the officer had left Long Island, just before he was to make detective, because he wanted to experience what it was like to work in “the big city.” Grimly, Frank replied, “Well, now he knows.”

At a coffee shop, Officer Walsh met Erin, who appealed to the cop’s own sense of parenthood in reflecting on Collins’ anger. She also asserted that she had enough prosecutorial experience to sense she hadn’t been told everything that happened, and she warned that Walsh would be under oath while testifying about her partner.

“You do what you gotta do,” the officer told Erin, “and I’ll do the same.”

The week’s Reagan-family dinner discussion revolved around police being like family … and around the “Blue Wall of Silence,” alleged to be upheld by cops to protect one another. Erin, Jamie and Danny (Donnie Wahlberg) debated how far that went, with Danny reasoning, “When you’re out in the street, the only one who can watch your back is your partner.”

After the meal, Erin told Frank she believed Cutter was “guilty of criminally negligent homicide.” Frank shot back that the case was “flimsy” and asked Erin what she’d do if the officer in question was one of her relatives. “Officer Cutter went too far,” she replied. “He needs to pay for it.”

At a bar, Danny and Jamie also were debating the case when other cops approached them and said of Cutter, “Your sister shouldn’t sell him out for a headline.” Fisticuffs almost ensued, and after all parties backed off, Danny told Jamie, “Reagans can talk smack all they want. Outsiders talk smack, there’s gonna be a fight.”

Wanting more background on Cutter, Frank went to talk to Valenti again, asking why Cutter would leave his old department when he was so close to getting his detective’s shield. Frank then added he knew about an allegation against Cutter that went away with his quick resignation.

“How’d you know?” Valenti asked. “I didn’t,” Frank responded. “Until now.”

Cornered, Valenti then told the full story of how Cutter had pursued a young felon who wound up with a fractured skull. “You let me hire a ticking time bomb,” Frank charged. “This goes public, I won’t cover for you. You’re on your own.”

Frank’s next visit was to Officer Walsh as she was walking her beat. “Sometimes,” he told her, “despite your best efforts, things go wrong.” He reminded her that her job is “to serve and protect … the citizens, and your partner,” and he said that while he respected her loyalty, whether Collins used excessive force was “for a jury to decide.”

Walsh then waited for Erin at the courthouse and apologized for not telling everything, admitting she did see Cutter put Collins in the ultimately fatal chokehold. Erin consoled Walsh that “what happened was not your fault” and added, “It takes a lot of courage to tell the truth.”

In their patrol car, Eddie decided to talk with Jamie about her father. “He ruined my family,” she said, and was the reason she always questioned her judgment — but she had decided that after her shift, she was going to the prison to see him, and she asked Jamie if he would go with her. “Yeah,” he said. “I could do that.”

When they got there, Eddie had second thoughts about going in, but Jamie told her that through the situations he’d shared with her, “You really showed me something. No matter what goes down, you never take a step back. You’re not afraid, Eddie.” She thanked him, and with a deep breath, into the prison she went.

Officer Cutter was informed by Frank that a grand jury was not going to indict him, and Frank commended him for starting a fund for Collins’ daughter. With a sigh of relief, Cutter said he was “just grateful I can get back to work.” “Not here,” Frank replied. “Not while I’m police commissioner.”

A shocked Cutter tried to plead his case, but Frank held firm, saying he had to decide whether an officer involved in two such incidents was “an unlucky one or a dangerous one. And I have to err on the side of caution here.” Declaring Cutter “not built for” using restraint, Frank concluded, “I’m sorry. You’re dismissed.”

Frank genuinely was sorry when he went to Erin’s office afterward, apologizing for having “reacted badly” upon learning she was handling the Cutter case. “You were doing your job, and I was only thinking of mine. I’m sorry.” A moved Erin thanked him, then suggested they go get drinks.

“Isn’t that some kind of conflict of interest?” Frank asked teasingly as they left. “Well,” Erin said, “we could get separate checks.”